The present invention is directed to a fast-acting electromagnetic valve, and more specifically to a low voltage, low current solenoid-driven valve for controlling molecular beams.
Supersonic molecular beams offer important advantages for the molecular spectroscopist. In addition to high sample density, supersonic expansion provides rotational and translational cooling of the sample which significantly simplifies its spectrum by reducing congestion from hot band adsorption.
However, one disadvantage of conventional, continuously flowing molecular beams is that they place a heavy load on the equipment vacuum system. In order to maintain a low background pressure in the interaction region, the apparatus for producing a continuous beam must be equipped for high gas loads and must incorporate one or more stages of differential vacuum pumping.
To overcome the problems involved in continuous beam devices, experiments using a high intensity pulsed laser crossed with a supersonic molecular beam have been reported. The low duty cycle of a pulsed laser eliminates the need for the unbroken duty cycle of the continuous molecular beam source, and under such circumstances, incorporation of a pulsed beam valve can dramatically reduce pumping requirements. Several designs for pulse valves mounted on vacuum systems with relatively modest pumping capacities are now in use in spectroscopy and scattering laboratories. However, such devices have required extremely high voltages and currents for operation, creating cooling problems. The high power levels and the need to provide sophisticated cooling systems made such devices bulky, inconvenient, and difficult to use. In addition, many prior devices created radio frequency interference problems in the sensitive measuring equipment which required additional shielding that added to the bulk of such devices.